Liquid crystal display (LCD) devices are characterized in that they are fabricated in a very thin form, are driven on a low voltage and consume only small quantities of power. Blessed with such features, a large number of LCD devices have been used extensively in various electronic apparatuses. Of these display devices, those particularly small in size have been adapted for use on electronic calculators and digital watches. In recent years, such small display devices are also finding their way into portable telephones.
For use on portable telephones, small-sized LCD devices are generally simple matrix LCD devices operating in one of two modes: twisted nematic (TN) mode, or super twisted nematic (STN) mode.
A simple matrix LCD device of a known type used on the portable telephone is an LCD module composed of an LCD panel and an LCD controller made of a single semiconductor integrated circuit to control the panel, the components being connected by a chip-on-glass (COG) arrangement.
More specifically, the chip-on-glass type LCD module has an LCD panel with liquid crystal interposed and sealed between a pair of glass substrates. On one of the two glass substrates constituting the LCD panel is an LCD controller (LSI) made of a single semiconductor integrated circuit.
The LCD controller-mounted glass substrate is formed integrally with liquid crystal output wires and input/output wires. The liquid crystal output wires are connected to liquid crystal output terminals of the LCD controller so that the controller may output liquid crystal driving voltages (segment and common voltages) to electrodes (segment and common electrodes) inside the LCD panel. The input/output wires are connected to input/output terminals of the LCD controller so that various signals are input to and output from the controller. The input/output wires are drawn to an edge of the controller-mounted glass substrate and connected there to a printed circuit board that comprises a central processing unit (CPU) and other components.
As outlined above, the chip-on-glass type LCD module has an LCD panel, an LCD controller (LSI), liquid crystal output wires and input/output wires, all mounted on a single glass substrate. This constitution contributes to making external dimensions of the LCD module smaller than before. This type of LCD module is discussed illustratively in Japanese Unexamined Patent Publication Nos. Hei 6-118433 and Sho 63-191130.
In the chip-on-glass type LCD module, the liquid crystal output wires formed on one of the paired glass substrates are connected directly to the LCD panel. The direct connection eliminates problems associated with the routing of the liquid crystal output wires.
In general, the input/output wires formed on one of the glass substrates are drawn out of the input/output terminals of the LCD controller (LSI) up to an edge of the glass substrate without being crossed halfway. If the arrangement of the input/output terminals of the LCD controller differs from the arrangement of the input/output terminals of the printed circuit board, then it becomes necessary to cross illustratively signal conductors and power supply wires. The signal conductors supply various signals to the LCD controller and receive output signals from the controller, and the power supply wires carry a supply voltage (VCC) or a reference potential (GND). The crossing of the wires and conductors, if carried out, necessitates complicated rerouting of the wiring inside the printed circuit board.
In this connection, an LCD controller (LSI) with mode terminals for changing its internal status (operation mode or device ID information) has a distinctive wiring characteristic. That is, all input/output wires including those connected to the mode terminals are drawn out, without crossing, to an edge of one of the glass substrates. The mode terminals are connected through the printed circuit board to its power supply wires carrying the supply voltage (VCC) or reference potential (GND) for the board in question, whereby the mode terminals are continuously pulled up to the supply voltage (VCC) or pulled down to the reference potential (GND).
In the above setup, it is necessary to install a large number of input/output wires on one of the glass substrates of the LCD module incorporating the LCD controller (LSI) having the mode terminals. The need to install the numerous wires complicates wiring patterns of the input/output wires and lowers degrees of freedom in arranging the wiring patterns. The interposed presence of the printed circuit board in such wiring further confounds rerouting arrangements.
It is therefore an object of the present invention to provide a liquid crystal display device and a method for fabricating the device, whereby the number of input/output wires connected to input/output terminals of a semiconductor integrated circuit is reduced so that patterns of input/output wiring are simplified and that degrees of freedom in arranging the input/output wiring patterns are enhanced.
It is another object of the present invention to provide a liquid crystal display device and a method for fabricating the device, whereby the number of input/output wires connected to input/output terminals of a semiconductor integrated circuit in the device is reduced so that the device as a whole has reduced external dimensions and that the cost of fabricating the device is lowered.
It is a further object of the present invention to provide a portable telephone such that its external dimensions are reduced and that the cost of fabricating the telephone is lowered through the use of an inventive liquid crystal display device.
Further objects and advantages of this invention will become apparent from a consideration of the accompanying drawings and ensuring description of it.